It is known from the prior art, for example WO 01/14599 A1, to arrange a plurality of oxygen nozzles at the periphery of a melting reduction assembly. In this way, it is possible to form a CO-containing and H2-containing reducing gas in a packed bed made from solid carbon carriers and ferrous input materials in the melting reduction assembly. However, in this type of arrangement of oxygen nozzles, the number of oxygen nozzles and therefore the maximum achievable melt output or pig iron production level is limited.
In melting reduction methods such as COREX and FINEX which have a melting reduction assembly, in particular a melter-gasifier, oxygen nozzles are installed at the periphery between the hearth and the char bed (packed bed, carbon bed) in order to blow in the oxygen as evenly as possible at the periphery for the gasification of carbon in order to form the reducing gas and to provide the required energy. It is also known to blow in fine coal via the oxygen nozzles in order to reduce the coal usage, in particular the use of pieces of coal or coal bricks.
Operating results have revealed that the melt output per oxygen nozzle is limited since both too much gas and too much liquid pig iron and liquid slag being formed can bring about insufficient permeability in front of and/or below and/or above the oxygen nozzle plane. This results in greater demands being placed on the raw materials used, so that suitable packed bed stability can nevertheless be achieved or secured. A further consequence is the limitation of the fine coal injection because this measure can also have a permeability-reducing effect, so that process faults, for example, limitation of the output or quality variations can be the result. Furthermore, insufficient drainage of the fluid phases (e.g. pig iron, slag) can also result in nozzle damage.
Previous operating results of systems of this type have shown that a relationship between the frequency of nozzle damage and the melt output per nozzle is probable. It has also been found that the fine coal quantity that can be blown in per nozzle is limited.
Different approaches to solutions have taken account of variations of the nozzle geometries. However, the results have so far not been satisfactory, particularly in systems with high pig iron production levels.
Development plans also exist which aim at a larger pig iron production level. Previously known arrangements of the oxygen nozzles in a nozzle plane and at the periphery of a melting reduction assembly lead, due to the size of the nozzle supports and the required thicknesses of the sheet metal in the gasifier metal shell between the nozzle supports, to a smaller number of oxygen nozzles and therefore to systems with output limitations or to process faults and reduced availability on account of nozzle faults.
Furthermore, an increase in the output of the melting reduction assembly can be achieved through an increase in the hearth area, that is, the inner cross-section of the melting reduction assembly, wherein the periphery does not increase to the same extent, so that limitations also arise in this regard.